Two types of mutants of Drosophila melanogaster are being used to study how genetic lesions induce paralysis. One class of mutants (bang-sensitive) exhibits a stress-induced paralysis while the second class (shibirets) exhibits a temperature-induced paralysis. Studies are in progress using genetic mosaics and an internal histochemical marking scheme to determine the focus of action of each of these mutants. In addition to temperature-induced paralysis, the shibire mutation also causes a series of temperature-induced abnormalities if cultures are exposed to the nonpermissive temperature at various times in development. We are using primary embryo cultures which allow us to follow the differentiation of neurons and myocytes. We will compare differentiation in wild-type and shibire cells to determine whether the mutation affects this differentiation process in terms of morphology. We will also determine whether there are observable differences in RNA transcription patterns between mutant and wild-type cells at the permissive and nonpermissive temperatures. BIBLIOGRAPHIC REFERENCES: Fan, C.L., L. M. Hall. A. J. Skrinska, and G. M. Brown (1976). Correlation of guanosine triphosphate activity and the synthesis of pterins in Drosophila melanogaster, Biochem. Genetics, in press. Feitelson, J.S. and L.M. Hall (1975). Genetic and behavioral analysis of stress-sensitive mutants of Drosophila melanogaster, Genetics 80, s30 (Abstract).